CI: Add gitlint commit-msg pre-commit hook

Wire commit-message linting consistently via the gitlint pre-commit
hook and run it from the pre-commit tox env so Jenkins tox-verify
exercises it. Aligns with the odlparent/releng-builder pattern.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Change-Id: Ic2887e689dc74ab69c8d9c038c85bbcd2dfe9a11
Signed-off-by: Anil Belur <abelur@linuxfoundation.org>

Author: askb

.pre-commit-config.yaml

@@ -29,6 +29,11 @@ repos:
         args: ["--fix=lf"]
         exclude: '^.*\.(bin|patch|diff|xml|XML|yang|YANG)$'
 
+  - repo: https://github.com/jorisroovers/gitlint
+    rev: acc9d9de6369b76d22cb4167029d2035e8730b98 # frozen: v0.19.1
+    hooks:
+      - id: gitlint
+
   - repo: https://github.com/Lucas-C/pre-commit-hooks
     rev: a30f0d816e5062a67d87c8de753cfe499672b959 # frozen: v1.5.5
     hooks:

tox.ini

@@ -1,8 +1,15 @@
 [tox]
 minversion = 1.6.0
-envlist = docs
+envlist = docs pre-commit
 skipsdist = true
 
 [testenv:docs]
 deps = -rdocs/requirements.txt
 commands = sphinx-build -W -n -b html -d {envtmpdir}/doctrees ./docs/ {envtmpdir}/html
+
+[testenv:pre-commit]
+basepython = python3
+deps = pre-commit
+commands =
+    pre-commit run --all-files
+    pre-commit run gitlint --hook-stage commit-msg --commit-msg-filename .git/COMMIT_EDITMSG